Change of Muscle Insertion Position after Disinsertion of Extraocular Muscles

ABSTRACT

PURPOSE: This study examines the change in distance from the corneal limbus to the insertion of the rectus muscles before and after disinsertion and retraction with a pair of fixation forceps during strabismus surgery. METHODS: In 38 strabismus patients, on 30 medial rectus muscles and 38 lateral rectus muscles, before and after disinsertion and retraction with a pair of fixation forceps, the distances from the corneal limbus to the upper, middle and lower parts of the insertion of the medial and lateral rectus muscles marked with methylene blue solution were measured. RESULTS: The distances between the corneal limbus and upper, middle and lower parts of the insertion after the disinsertion were reduced on, average 0.23 mm, 0.28 mm, and 0.18 mm, for the medial rectus muscle, respectively, and 0.21 mm, 0.28 mm, and 0.15 mm, for the lateral rectus muscle, respectively (P<0.05). The percentage of cases in which the advance from the corneal limbus to the insertion was greater than 0.5 mm was 33.3% for the medial rectus muscle, and 21.1% for the lateral rectus muscle. The lateral rectus muscle was disinserted, fixed with a pair of forceps, and subsequently, the distance from the upper, middle and lower parts to the corneal limbus were reduced to 0.36 mm, 0.43 mm, and 0.30 mm, respectively (P<0.05). The percentage of cases that advanced more than 1.0 mm was 13.2 %. The changes in distance from the upper, middle, and lower parts of insertion toward the limbus after disinsertion and retraction were 0.15 mm 0.15 mm, 0.16 mm, respectively (P<0.05). CONCLUSIONS: When performing the recession of the lateral rectus muscle, disinsertion of the rectus muscle, may result in a change of the site of insertion, which in turn might influence the outcome of strabismus surgery.